It was reported that after being made a full-time employee in October last year, her workload increased drastically. For example, her overtime from 9 October to 7 November was of 105 hours.

According to media reports, prior to committing suicide, Matsuri started posting tweets in October last year, suggesting an intention to kill herself.

The Tokyo Reporter says she would tweet about days where she would only get 2 hours of sleep and that she "would rather die if this went on" and "death would be bliss."

A tweet dated 21 November 2015, on Matsuri's account, reads, "I'm a newcomer 23-year-old OL [Office lady] who has fallen into transmigration, where no matter how late I come home, I have to search for new cat videos for an hour every night or else I can't sleep. My biggest worry is the residence tax starting next June, and what I look forward to every month is going to Tsukiji for sushi alone on pay day."

And on 16 December 2015, Matsuri tweeted, "Thinking I want to die every day, each of them being this stressful. I wonder what lies ahead if I overcome them."

According to records, the young victim logged 130 hours of overtime in just one month and had 10 hours of sleep in a week

Dentsu recognised that Matsuri worked about 105 overtime hours a month.

However, as a result of such a work culture, the young woman developed depression by early November and eventually needed extreme effort to do her job, according to a government labour agency, the Mita Labour Standard Inspection Office.

Now, after about 9 months, Matsuri Takahashi's suicide has been recognised as karoshi, meaning death from overwork, according to decision by the Mita Labour Standard Inspection Office on 30 September, the findings of which were disclosed by family members and lawyers at a news conference in Tokyo on 7 October 2016

Matsuri's mother speaking to reporters at the health ministry on Friday, 7 October.

The Mita inspection office recognised that the volume of Matsuri's workload increased sharply and her overtime work shot up drastically, concluding that she suffered a mental breakdown due to the psychological burden of so much overtime and took her life.

Matsuri's mother, Yukimi Matsuri, while lamenting that her daughter will never return despite the recognition of her death as having been work related, called for serious improvements in labour management in Japan and asked the government to supervise companies appropriately to prevent further deaths from overwork.

"My daughter was telling her friends and colleagues she would get only 10 hours of sleep in a single week and the only thing she felt was just a desire to sleep…Why did she have to die?" the 53-year-old mother was quoted as saying.

"No job could be more important than life. I strongly hope for the central government to instruct businesses as soon as possible," she told reporters.

While Dentsu said it is taking the death of the employee seriously, reports say the advertising giant had also bullied her by saying such things as "your 20 hours of overtime is useless to this company"

According to tweets posted on 31 October 2015, her department head said:

"Putting on a sleepy face during meetings means lack of management. Your hair is a mess, and don't come to work with your eyes all red. For you to be struggling with this amount of work means a total lack of capacity."

It was reported Matsuri, who studied hard to make her divorced mother's life easy, was an upbeat girl. However, comments she posted on social media starting last October became markedly downbeat, showing how the overtime and power harassment at Dentsu was affecting her. Some of her comments included views, like, "My body and mind are in tatters," and "I've lost all feeling except for the wish to sleep."

This case involving Dentsu is far from unique, though. In 2013, a young employee at Y&R in Indonesia died as a result of overwork.